First published online November 9, 2007
Development 134, 2302e (2007)
© The Company of Biologists Limited
Pre-implantation patterning by chance?
During pre-implantation mammalian development, a blastocyst forms that
contains three distinct cell types: trophectoderm (which gives rise to the
placenta) and the primitive endoderm and epiblast (which together form the
inner cell mass from which the fetus develops). But does blastocyst patterning
originate in the egg (the prepatterning model) or do differences between
blastomeres only appear after the 8-cell stage of embryonic development (the
regulative model)? On p.
4219, Dietrich and Hiiragi now provide evidence that patterning in
pre-implantation mouse embryos involves stochastic (random) processes. To
identify the critical events in blastocyst patterning, the researchers
analyzed the expression of Oct4, Cdx2 and Nanog (three transcription factors
that help to specify the blastocyst lineages) at precisely defined times
during pre-implantation development. Their results lead them to propose a
regulative model for blastocyst patterning in which the first lineages in the
early mouse embryo emerge after the 8-cell stage as a result of random
processes and/or of earlier asymmetric cell divisions.
Related articles in Development:
- Stochastic patterning in the mouse pre-implantation embryo
- Jens-Erik Dietrich and Takashi Hiiragi
Development 2007 134: 4219-4231.
[Abstract]
[Full Text]
